如果任何参数为 NULL，MySQL EXPORT_SET() 函数返回什么？
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王林
转载
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2023-09-02 20:17:02
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如果 MySQL EXPORT_SET() 函数中提供的任何参数为 NULL，则该函数将返回 NULL。以下示例将演示它 -
mysql> Select EXPORT_SET(NULL, 'Y','N',',', 4);
+----------------------------------+
| EXPORT_SET(NULL, 'Y','N',',', 4) |
+----------------------------------+
| NULL |
+----------------------------------+
1 row in set (0.00 sec)
mysql> Select EXPORT_SET(5, NULL,'N',',', 4);
+--------------------------------+
| EXPORT_SET(5, NULL,'N',',', 4) |
+--------------------------------+
| NULL |
+--------------------------------+
1 row in set (0.00 sec)
mysql> Select EXPORT_SET(5, 'Y','N',',', NULL);
+----------------------------------+
| EXPORT_SET(5, 'Y','N',',', NULL) |
+----------------------------------+
| NULL |
+----------------------------------+
1 row in set (0.00 sec)
mysql> Select EXPORT_SET(5, 'Y','N',NULL, 4);
+--------------------------------+
| EXPORT_SET(5, 'Y','N',NULL, 4) |
+--------------------------------+
| NULL |
+--------------------------------+
1 row in set (0.00 sec)
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